The present invention relates to infusion catheters for delivery of therapeutic fluids to bodily passages, and particularly to infusion catheters exhibiting uniform distribution of such therapeutic fluids along a length of the catheter.
In certain medical conditions, it is advantageous to deliver a therapeutic agent directly to a target region to avoid medicating the entire body and to limit the amount of therapeutic agent required for effective treatment. One example of such a medical condition is an arterial thrombus, or clot, which can be treated effectively by localized application of such therapeutic fluids as those containing tissue plasminogen activator, urokinase, or streptokinase.
Infusion catheters have been developed which can deliver therapeutic fluids directly to affected bodily passages, for example a thrombotic region of an artery. One type of infusion catheter is a hollow tube, the distal end of which has been pierced through its side wall to form multiple openings, or ports, providing direct access to the exterior for fluid flowing through a common central lumen. The ports are disposed at several axial positions along the infusion section to provide distribution of the therapeutic fluid along a desired length of the bodily passage. However, fluids flowing through a tube flow more readily from ports offering the least flow resistance. The longer the flow path followed by the fluid in the central lumen, the higher the resistance and the higher the pressure drop (.DELTA.P) in the fluid. If the infusion section of this catheter is more than a few centimeters long, the fluid flowing from each port exhibits resistance and a .DELTA.P proportional to the fluid flow distance along the length of the central lumen. Thus, the fluid flowing to the more distal ports experiences higher .DELTA.P than that flowing to the more proximal ports, and the-fluid distribution is not uniform.
In another type of infusion catheter, the wall of the infusion section includes several small axial lumens each with a single opening or port to provide direct access to the exterior of the catheter for fluid flowing through each small lumen. The ports are disposed at different axial lengths along the infusion section to provide distribution to the desired length of the bodily passage. This design offers some improvement in distribution, but the varying lengths of the fluid flow paths still result in non-uniform flow over the length of the infusion section. Also, in this design the number of fluid delivery ports is limited by the small circumference of the infusion section tube.
It would be desirable to have an infusion catheter having an infusion section in which the resistance, or .DELTA.P, experienced by the fluid flowing to all the ports is equalized or balanced to provide uniform distribution of fluid along a desired length of a bodily passage. The infusion catheter described herein was developed to address that need.